In the traditional mobile phone roaming procedure, communication links have to be established between the mobile networks both in the home region and in the roaming region to support calls of mobile subscribers in roaming state and to enable mobile subscribers in roaming state to use diverse telecom services, such as initiating calls or answering calls, etc. However, since communication route is long and more network resources are consumed in roaming state, the service cost in roaming state is higher than that in normal state. Especially, in international roaming state, any call to the subscriber is international toll call, i.e., the call has to be accomplished through the voice path between the mobile network in the home country and that in the roaming country; therefore, the roaming subscriber has to pay the international toll cost from the home country to the roaming country; even though the caller is within a stone's throw to the roaming subscriber (e.g., when two members in a tourist party are calling in a roam region), both parties have to pay the toll for international call. As a result, the communication demand of roaming subscribers is suppressed by the expensive cost. Therefore, people are eager to implement localized roaming of mobile phones to decrease expensive roaming call cost.
However, the traditional mobile networks can't meet such a demand. The structure of a typical traditional mobile network is shown in FIG. 1. As shown in the network in home country in FIG. 1, the network entities related to mobile phone roaming processing in a traditional network include a Base Transceiver Station (BTS), a Base Station Controller (BSC), a Mobile Switching Center (MSC), a Visiting Location Register (VLR) and a Home Location Register (HLR). For example, when the subscriber's mobile phone is roaming in different countries, the mobile phone has to use its number N in the home country wherever it is because the number of the mobile phone N is stored in the HLR of the subscriber's home network. A call to the roaming subscriber has to be switched to the home country of the subscriber, so that the MSC in the subscriber's home country can query HLR in the home country about the route and establish the voice path to the roaming country. However, in many cases, this is unnecessary; for example, when the caller is in the roaming country where the called subscriber is or a call is initiated from the third country except for the home country or the roaming country where the called subscriber is. Even though it is unnecessary, the roaming subscriber has to bear the charge for international toll call from the home country to the roaming country.
The reason for above case lies in the process to called number by the switching device. An international call is first routed to a gateway office in the called subscriber's home country, herein a further determination for the called number's property; if it is a mobile phone number, the call is routed to GMSC in the mobile network for subsequent process. Each country has its independent numbering scheme, so switching devices in one country cannot determine number properties of other countries, i.e., the called is a telephone or mobile phone, because this requires a large quantity of configuration data, and it is more important that change of numbering scheme in each country will affect other countries, and this will cause numbering schemes in countries lack of independence.
For solving said problem, the mobile subscriber can use a local number in a roaming region/network. Viewed from the point of the roaming region/network, some local mobile phone numbers are allocated for foreign subscribers roaming in the region/network. And the roaming subscriber can share local services using the local number.